The former US president Bill Clinton yesterday travelled to North Korea, the most insular nation on Earth, on a surprise mission to seek the release of two US journalists who were imprisoned in March for straying into North Korea while on assignment in China.

Within hours of a face-to-face meeting with its ruler Kim Jong-il, Laura Ling and Euna Lee, sentenced in June to 12 years hard labour for engaging in “hostile acts”, had been granted a special pardon.

In Pyongyang, Mr Clinton was ushered into talks with Mr Kim, the so-called “Dear Leader” of the secretive state which George Bush included in his “Axis of Evil”.

The breakthrough will bring relief to the journalists’ families, but Mr Clinton’s mission also appeared to have a broader agenda. Arranged in secrecy, it had all the appearance of an enormous diplomatic gamble. North Korea has the capacity ? and the paranoia ? to deliver to Barack Obama the biggest foreign crisis of his presidency. It has tested a large nuclear device and long-range missiles. Japan is in range. Alaska and Hawaii almost are.

No one was fooled by the shoulder-shrugging of the White House after the news broke of Mr Clinton’s arrival in an unmarked plane to seek the release of the duo from their incarceration in the secretive communist state.

It was a “private” mission, aides insisted, and they denied reports in the official North Korean media that he had “courteously” delivered a verbal message to Mr Kim from Mr Obama.

But the last time an American official met Mr Kim was in 2000. This was not something that just happened, without lengthy preparations, not to say agonising, by both sides.

There was a reception committee waiting for Mr Clinton when he landed, consisting of the Vice Foreign Minister Kim Kye Gwan, who has been chief nuclear negotiator in the past, and a girl with flowers. Television images released within hours showed Mr Clinton sitting at a negotiating table with the North Korean leader.

That he was granted a swift audience was already a good omen for the two women, Laura Ling, 32, and Euna Lee, 36, who, on assignment for San Francisco’s Current TV, were arrested for allegedly erring on to North Korean soil while at the border with China, where they were reporting about women fleeing the prison state. But much more was potentially at stake than the pair’s liberty.

Last night, North Korean state media said the pardon was a sign of the “humanitarian and peace-loving policy” that Pyongyang pursued. It said that Mr Clinton had apologised for the women’s conduct: “Clinton expressed words of sincere apology to Kim Jong-il for the hostile acts committed by the two American journalists against the DPRK after illegally intruding into it.”

But did Messrs Clinton and Kim sit at that table with their dour-faced aides and pose for propaganda photographs without discussing other matters that are outstanding?

The US desperately wanted the women released. But much more, it wants North Korea to stop its dangerous nuclear posturing, to return to international talks on disarming itself and cease proliferating weapons of mass destruction. State media said in a report that the two men had indeed engaged in “exhaustive talks” on a range of topics.

And opportunities like this to peer inside North Korea ? and into the eyes of Mr Kim, who, at 67, is known to be in faltering health after a reported stroke last year ? do not come often. Analysts in the US ache for new pictures of the man to gauge his health.

It is unlikely that the deeply delicate topic of the succession came up directly. The West believes Mr Kim favours handing power to his 26-year-old Swiss-educated son, Kim Jong-un.

But whether the successful mission indeed held the promise of easing all the re-accumulated tensions between Pyongyang and Washington (and Seoul), it was the choice of envoy that was intriguing.

Mr Clinton was dogged by North Korea while in office, wavering between threatening war and then doing deals ? deals to trade aid for suspensions in North Korea’s nuclear doings that eventually fell apart.

In recent weeks, there had been speculation that Al Gore, a co-founder of Current TV, or the New Mexico Governor, Bill Richardson, would be chosen to embark on a mission to negotiate a release for the two journalists.

Hillary Clinton, the US Secretary of State, was en route to Africa early yesterday when she confirmed to the small group of reporters who were travelling with her that her husband was at the unfriendly end of the Korean peninsula.

An unanswered question remained why, if she has been fretting recently about her fading profile, she had apparently sub-contracted a mission of such scale to her husband.

It was not so long ago that the foreign policy community was wondering out loud about the wisdom of choosing Mrs Clinton as Secretary of State precisely because of the obstacles posed by the man she called husband. They worried about conflicts of interest with Mr Clinton’s travels on behalf of his international foundation. Would he embarrass her, perhaps by tapping undesirable potentates for money?

Now there is a different scenario, where Mr Clinton serves as a crucial ambassador abroad for Mr Obama’s foreign policy priorities.

The threading of Democratic presidents who have been past through the eye of the Pyongyang needle is also arresting. The best hope of a breakthrough for Mr Clinton came in 1994 when he sent an envoy of his own there ? Jimmy Carter. Mr Carter, who met Mr Kim’s father, Kim Il-sung, was building his own career as special envoy for Uncle Sam.

Last night’s extraordinary breakthrough and the abrupt freeing of the two reporters will bring their distraught families joy and much yearned-for relief. Ms Ling has an unidentified medical condition that needs attention while Ms Lee has a four-year-old daughter.

What benefits the deal could bring in easing tensions between the US and North Korea on the full range of difficulties may not become obvious for weeks or months to come.

Pyongyang has taken one step after another of late to aggravate the US, which, in turn, led efforts at the United Nations to turn up sanctions. The North Koreans have also withdrawn from six-party talks on suspending its nuclear programmes and vowed never to return.

The White House insists that the plight of the women was being treated completely separately from its other problems with North Korea.

But the mere fact of Mr Clinton being in Pyongyang and speaking to the North Korean leadership, a great prize for them, may become a precursor to a dialogue, possibly even to a resumption of the six-party negotiations. Thanks to the two reporters and their steps into North Korean territory, both sides see a chance to gain leverage on one another.

US and North Korea: Trading insults

Kim Jong-il may have been all smiles and handshakes with Bill, but just a few days ago his regime was in something of a slanging match with the other Clinton.

On a recent visit to New Delhi, Hillary, the Secretary of State, bemoaned the North Korean leadership’s “constant demand for attention,” before adding: “Maybe it’s the mother in me or the experience that I’ve had with small children and unruly teenagers.”

The North Koreans’ response was firm. “We cannot but regard Mrs Clinton as a funny lady as she likes to utter such rhetoric, unaware of the elementary etiquette in the international community,” a spokesperson said. “Sometimes she looks like a primary schoolgirl and sometimes like a pensioner going shopping.”

The name-calling between Washington and Pyongyang is not new. George W Bush branded Kim Jong-il “a spoiled child at a dinner table”. The North Koreans called Bush a “tyrannical imbecile” lacking “even an iota of elementary reason”. And in 1968, North Korea’s Major-General Pak Chung Kuk called Lyndon Johnson a “living corpse”.

Explainer: The diplomatic background

Q. So who exactly are Euna Lee and Laura Ling?

A. The two women are American journalists who work for Al Gore’s Current TV. Ling, an on-air reporter for the show Vanguard who has worked in Vietnam, Mexico and China, hails from California; Lee, a video producer, is originally from South Korea. The two were arrested on the North Korean border with China and charged with spying and, until their special pardon was issued last night, they faced 12 years of hard labour.

Q. What other issues are at stake between the US and North Korea?

A. The elephant in the room throughout is the question of North Korea’s nuclear arms programme. The country has engaged in a drastic escalation of its efforts to obtain a nuclear weapon, a move seen by many as a ploy to gain more attention from the West. It already has enough material for six to eight nuclear weapons, but there is no evidence of a working bomb. Clinton’s visit offers useful cover for negotiations on the subject.

Q. Why was Clinton picked to make the trip to Pyongyang?

A. The choice of the Secretary of State’s husband was a surprise to many, after rumours that former vice-president and Current TV founder Al Gore was primed to make the visit. But Clinton has undoubted authority on the international stage, and his relationship with Hillary means that the White House can claim the trip is at arms length but retain an official stamp.

Q. Are there any precedents for Clinton’s mission?

A. Jimmy Carter visited North Korea when Clinton was President, but that mission lacked the White House’s endorsement. And Clinton’s position as a former president with a spouse within the administration is unique. If the trip, Clinton’s first in a diplomatic role since Obama took power, is seen as a success, he may well take on similar missions in the future.